Connecticut · Connecticut Public Health Code Section 19-13-B103
The Connecticut Department of Public Health sets the code; local health departments and districts issue permits for systems under 5,000 gallons per day.
Minimum tank
One to three bedroom dwelling.
Design flow
Held two days for settling.
Cost index
Regional labour and permits.
Sets the design flow and the legal minimum.
Code sizes on bedrooms, not people.
Used to size the matching drainfield. Unsure? Sandy loam is the common default.
Glacial till and outwash over bedrock. Ledge rock at shallow depth is common, seasonal high groundwater is widespread, and many lots are small with wells nearby, so setbacks bind before soil does.
Conventional trenches and galleries where depth allows. Fill systems and curtain drains are routine responses to shallow ledge and high water table.
| Dwelling | Design flow | Minimum tank | With disposal |
|---|---|---|---|
| 1 bedroom | 300 gpd | 1,000 gal | 1,250 gal |
| 2 bedrooms | 300 gpd | 1,000 gal | 1,250 gal |
| 3 bedrooms | 450 gpd | 1,000 gal | 1,250 gal |
| 4 bedrooms | 600 gpd | 1,250 gal | 1,500 gal |
| 5 bedrooms | 750 gpd | 1,500 gal | 1,750 gal |
Connecticut requires deep test pits and percolation tests witnessed by the local health department, typically in the wet season. Small lot sizes make well and property line setbacks the practical constraint on many parcels.
The state sets a floor. These Connecticut counties are where the largest septic populations sit, and where local requirements most often exceed it.
| County | What makes it different |
|---|---|
| Hartford | Central valley soils, mixed conditions |
| New Haven | Dense development, small lots, tight setbacks |
| Fairfield | High-value rural lots with ledge rock |
| Litchfield | Rocky uplands, large lots, shallow bedrock |
| New London | Coastal and eastern soils, high water table near shore |
A three-bedroom home at 150 gallons per bedroom produces 450 gallons per day of design flow. On sandy loam that needs roughly 750 square feet of absorption area. On clay loam it rises to about 2,250 square feet, and on clay a conventional field is usually not permitted at all. Run your own soil class through the drainfield calculator.
Local health departments commonly require inspection at property transfer. Use the pump schedule calculator to work out the interval for your tank size and household.
Regional labour and permit costs in Connecticut run about 125% of the national baseline. Here is what typical installations land at for a three-bedroom home:
| System type | Typical installed cost in Connecticut | When it applies |
|---|---|---|
| Conventional gravity | $11,200 – $20,000 | Good soil, adequate depth to water |
| Chamber system | $12,300 – $23,000 | Alternative to gravel trenches |
| Mound system | $21,300 – $42,000 | Shallow water table or thin soil |
| Aerobic treatment | $17,900 – $36,000 | Clay soil or small lots |
| Tank pump-out (service) | $400 – $810 | Every 3–5 years |
Replacing an existing system costs more than these figures — old-system removal and re-permitting add to every line. The replacement cost calculator covers that case, and the cost estimator adjusts all of the above for your bedroom count and soil.
Verify before you build. The figures above are state minimums compiled for planning, drawn from Connecticut Public Health Code Section 19-13-B103, Subsurface Sewage Disposal. County and health district rules routinely exceed them, code text changes, and only Connecticut DPH — Subsurface Sewage Disposal or your local health department can confirm what applies to your parcel.
Send your sizing numbers to installers who work under Connecticut rules every day.